Effect of graded hypoxia on hepatic tissue oxygenation measured by near infrared spectroscopy

Background/Aims: In liver transplantation ischaemia-reperfusion injury of t he graft reduces hepatic tissue oxygenation which has prognostic value for patient survival, Near infrared spectroscopy (NIRS) can measure extracellul ar (haemoglobin oxygenation) and intracellular tissue oxygenation (cytochro me oxidase oxidation), However, it has not been validated for measuring hep atic tissue oxygenation in an experimental model with graded hypoxia, Methods: New Zealand White rabbits (2,9+/-0,3 kg, n = 9) underwent laparoto my for liver exposure, Heart rate, blood pressure, temperature, arterial bl ood pH and blood gas partial pressures were monitored during the experiment s, Near infrared spectroscopy probes were placed on the liver surface to re cord continuously hepatic oxyhaemoglobin, deoxyhaemoglobin and cytochrome o xidase oxidation, Graded hypoxia was achieved by stepwise reduction of the inspired oxygen from 15 to 4%, During recovery from hypoxia 30% oxygen was administered, Results: There was an immediate reduction of hepatic oxyhaemoglobin with hy poxia and a simultaneous increase of hepatic deoxyhaemoglobin, Hepatic oxyh aemoglobin showed a positive correlation with arterial oxygen pressure (r=0 .77, p<0,001), Hepatic deoxyhaemoglobin showed a negative correlation with arterial oxygen pressure (r=-0.75, p<0,001), Hepatic cytochrome oxidase dec reased significantly with an inspired oxygen of 10% or less and showed a po sitive correlation with arterial oxygen pressure (r = 0,90, p<0,001), Conclusions: Near infrared spectroscopy is an effective method for monitori ng hepatic extracellular and intracellular tissue oxygenation.